This invention relates to an informtion transmission system for railway vehicles which is enhanced in reliability.
Various kinds of electric control devices are installed on the cars of trains. In recent years, it has been developed to transmit by optical fibers information as to whether or not the control devices are normally operating and how they are operating.
As illustrated in FIGS. 1(A) and 1(B), many of optical transmission lines for vehicular information adopt a dual loop organization because of the properties thereof. It is recognized by way of example that, when any fault of the transmission line has occurred during the transmission of information with a normal loop as shown in FIG. 1(A), the path is automatically changed-over to a stand-by loop as shown in FIG. 1(B) so as to minimize the loss of the transmission function. Since, however, the change-over of the paths is effected after the confirmation of the disconnection or the like of the path, the period of time during which the function is lost becomes long. When this period of time is intended to be curtailed, the period of time for acknowledging the occurrence of the fault is shortened, with the result that the unnecessary and erroneous change-over of the paths increases.